Add example for custom time with database/sql (#133)

driver/driver.go

@@ -8,6 +8,8 @@
 //
 // The data source name for "sqlite3" databases can be a filename or a "file:" [URI].
 //
+// # Default transaction mode
+//
 // The [TRANSACTION] mode can be specified using "_txlock":
 //
 //	sql.Open("sqlite3", "file:demo.db?_txlock=immediate")
@@ -18,6 +20,8 @@
 //   - a [serializable] transaction is always "immediate";
 //   - a [read-only] transaction is always "deferred".
 //
+// # Working with time
+//
 // The time encoding/decoding format can be specified using "_timefmt":
 //
 //	sql.Open("sqlite3", "file:demo.db?_timefmt=sqlite")
@@ -27,6 +31,28 @@
 //   - "sqlite" encodes as SQLite and decodes any [format] supported by SQLite;
 //   - "rfc3339" encodes and decodes RFC 3339 only.
 //
+// If you encode as RFC 3339 (the default),
+// consider using the TIME [collating sequence] to produce a time-ordered sequence.
+//
+// To scan values in other formats, [sqlite3.TimeFormat.Scanner] may be helpful.
+// To bind values in other formats, [sqlite3.TimeFormat.Encode] them before binding.
+//
+// When using a custom time struct, you'll have to implement
+// [database/sql/driver.Valuer] and [database/sql.Scanner].
+//
+// The Value method should ideally serialise to a time [format] supported by SQLite.
+// This ensures SQL date and time functions work as they should,
+// and that your schema works with other SQLite tools.
+// [sqlite3.TimeFormat.Encode] may help.
+//
+// The Scan method needs to take into account that the value it receives can be of differing types.
+// It can already be a [time.Time], if the driver decoded the value according to "_timefmt" rules.
+// Or it can be a: string, int64, float64, []byte, nil,
+// depending on the column type and what whoever wrote the value.
+// [sqlite3.TimeFormat.Decode] may help.
+//
+// # Setting PRAGMAs
+//
 // [PRAGMA] statements can be specified using "_pragma":
 //
 //	sql.Open("sqlite3", "file:demo.db?_pragma=busy_timeout(10000)")
@@ -34,7 +60,8 @@
 // If no PRAGMAs are specified, a busy timeout of 1 minute is set.
 //
 // Order matters:
-// busy timeout and locking mode should be the first PRAGMAs set, in that order.
+// encryption keys, busy timeout and locking mode should be the first PRAGMAs set,
+// in that order.
 //
 // [URI]: https://sqlite.org/uri.html
 // [PRAGMA]: https://sqlite.org/pragma.html
@@ -43,6 +70,7 @@
 // [serializable]: https://pkg.go.dev/database/sql#TxOptions
 // [read-only]: https://pkg.go.dev/database/sql#TxOptions
 // [format]: https://sqlite.org/lang_datefunc.html#time_values
+// [collating sequence]: https://sqlite.org/datatype3.html#collating_sequences
 package driver
 
 import (
@@ -584,7 +612,8 @@ func (r *rows) Next(dest []driver.Value) error {
 }
 
 func (r *rows) decodeTime(i int, v any) (_ time.Time, ok bool) {
-	if r.tmRead == sqlite3.TimeFormatDefault {
+	switch r.tmRead {
+	case sqlite3.TimeFormatDefault, time.RFC3339Nano:
 		// handled by maybeTime
 		return
 	}

driver/example_test.go

@@ -6,12 +6,16 @@ package driver_test
 
 import (
 	"database/sql"
+	"database/sql/driver"
 	"fmt"
 	"log"
 	"os"
+	"time"
 
+	"github.com/ncruces/go-sqlite3"
 	_ "github.com/ncruces/go-sqlite3/driver"
 	_ "github.com/ncruces/go-sqlite3/embed"
+	_ "github.com/ncruces/go-sqlite3/vfs/memdb"
 )
 
 var db *sql.DB
@@ -149,3 +153,129 @@ func addAlbum(alb Album) (int64, error) {
 	}
 	return id, nil
 }
+
+func Example_customTime() {
+	db, err := sql.Open("sqlite3", "file:/time.db?vfs=memdb")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec(`
+		CREATE TABLE data (
+			id INTEGER PRIMARY KEY,
+			date_time TEXT
+		) STRICT;
+	`)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// This one will be returned as string to [sql.Scanner] because it doesn't
+	// pass the driver's round-trip test when it tries to figure out if it's
+	// a time. 2009-11-17T20:34:58.650Z goes in, but parsing and formatting
+	// it with [time.RFC3338Nano] results in 2009-11-17T20:34:58.65Z. Though
+	// the times are identical, the trailing zero is lost in the string
+	// representation so the driver considers the conversion unsuccesful.
+	c1 := CustomTime{time.Date(
+		2009, 11, 17, 20, 34, 58, 650000000, time.UTC)}
+
+	// Store our custom time in the database.
+	_, err = db.Exec(`INSERT INTO data (date_time) VALUES(?)`, c1)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var strc1 string
+	// Retrieve it as a string, the result of Value().
+	err = db.QueryRow(`
+		SELECT date_time
+		FROM data
+		WHERE id = last_insert_rowid()
+	`).Scan(&strc1)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("in db:", strc1)
+
+	var resc1 CustomTime
+	// Retrieve it as our custom time type, going through Scan().
+	err = db.QueryRow(`
+		SELECT date_time
+		FROM data
+		WHERE id = last_insert_rowid()
+	`).Scan(&resc1)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("custom time:", resc1)
+
+	// This one will be returned as [time.Time] to [sql.Scanner] because it does
+	// pass the driver's round-trip test when it tries to figure out if it's
+	// a time. 2009-11-17T20:34:58.651Z goes in, and parsing and formatting
+	// it with [time.RFC3339Nano] results in 2009-11-17T20:34:58.651Z.
+	c2 := CustomTime{time.Date(
+		2009, 11, 17, 20, 34, 58, 651000000, time.UTC)}
+	// Store our custom time in the database.
+	_, err = db.Exec(`INSERT INTO data (date_time) VALUES(?)`, c2)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var strc2 string
+	// Retrieve it as a string, the result of Value().
+	err = db.QueryRow(`
+		SELECT date_time
+		FROM data
+		WHERE id = last_insert_rowid()
+	`).Scan(&strc2)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("in db:", strc2)
+
+	var resc2 CustomTime
+	// Retrieve it as our custom time type, going through Scan().
+	err = db.QueryRow(`
+		SELECT date_time
+		FROM data
+		WHERE id = last_insert_rowid()
+	`).Scan(&resc2)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("custom time:", resc2)
+	// Output:
+	// in db: 2009-11-17T20:34:58.650Z
+	// scan type string: 2009-11-17T20:34:58.650Z
+	// custom time: 2009-11-17 20:34:58.65 +0000 UTC
+	// in db: 2009-11-17T20:34:58.651Z
+	// scan type time: 2009-11-17 20:34:58.651 +0000 UTC
+	// custom time: 2009-11-17 20:34:58.651 +0000 UTC
+}
+
+type CustomTime struct{ time.Time }
+
+func (c CustomTime) Value() (driver.Value, error) {
+	return sqlite3.TimeFormat7TZ.Encode(c.UTC()), nil
+}
+
+func (c *CustomTime) Scan(value any) error {
+	switch v := value.(type) {
+	case nil:
+		*c = CustomTime{time.Time{}}
+	case time.Time:
+		fmt.Println("scan type time:", v)
+		*c = CustomTime{v}
+	case string:
+		fmt.Println("scan type string:", v)
+		t, err := sqlite3.TimeFormat7TZ.Decode(v)
+		if err != nil {
+			return err
+		}
+		*c = CustomTime{t}
+	default:
+		panic("unsupported value type")
+	}
+	return nil
+}

driver/json_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func Example_json() {
-	db, err := driver.Open("file:/test.db?vfs=memdb")
+	db, err := driver.Open("file:/json.db?vfs=memdb")
 	if err != nil {
 		log.Fatal(err)
 	}

driver/savepoint_test.go

@@ -10,7 +10,7 @@ import (
 )
 
 func ExampleSavepoint() {
-	db, err := driver.Open("file:/test.db?vfs=memdb")
+	db, err := driver.Open("file:/svpt.db?vfs=memdb")
 	if err != nil {
 		log.Fatal(err)
 	}